The present invention is drawn to phase shifting plasma electromagnetic waveguides and plasma electromagnetic coaxial waveguides that are reconfigurable, durable, stealth compatible, and flexible. Additionally, various plasma waveguide horn antennas are also disclosed.
A waveguide is generally configured such that current and voltage distributions can be represented by one or more traveling waves, usually in the same direction. In other words, the traveling wave patterns in current and voltage are generally uniform.
A waveguide can be likened unto a coaxial line having the central conductor removed. These waveguides, despite the absence of the central conductor, are still capable of carrying higher frequency electromagnetic waves. Therefore, an important use of waveguides in general is for the transmission of high frequency power, e.g., coupling a high-frequency oscillator to an antenna. Although high frequencies may be transmitted along coaxial cable, a waveguide is generally better than coaxial lines for transmitting large amounts of high frequency signal. If the goal is to transmit lower frequency electromagnetic waves, coaxial lines are generally better. However, only a maximum amount of power may be transmitted along a coaxial line due to the breakdown of the insulation (solid or gas) between the conductors. Additionally, energy is often lost in the insulating material that supports the center conductor.
Whether dealing with metal waveguides or metal coaxial lines, there are serious limitations as to what frequency of waves may be propagated. This is in part due to the material that has been traditionally used to in the construction of waveguides. For example, since metal has fixed properties, a metal waveguide is only capable of propagating very specific signals. This is likewise true to some extent with coaxial cables or lines.
In addition, horn antennas have been widely used as a feed element for large radio astronomy, satellite tracking, and communications dishes found installed throughout the world. With horns, in addition to their utility for feeding reflectors or lenses, they are commonly used as elements in phased arrays, and can be used as a universal standard for calibration and gain measurements of other high-gain antennas. The widespread use of the horn antenna stems from its simplicity in construction, ease of excitation, versatility, large gain, and preferred overall performance. Such horns can take many forms including E-plane horns, H-plane horns, pyramidal horns, corrugated horns, aperture-matched horns, multimode horns (such as the diagonal horn and dual mode conical horns), dielectric-loaded horns, monopulse horns, and phase center horns. Often, a horn antenna is at the terminal end of a waveguide wherein the waveguide is flared to form the horn shape.
Gas has been used as an alternative conductor to metal in various applications. In fact, in U.S. Pat. No. 5,594,456, a gas filled tube coupled to a voltage source for developing an electrically conductive path along a length of the tube is disclosed. The path that is created corresponds to a resonant wavelength multiple of a predetermined radio frequency. Though the emphasis of that patent is to transmit short pulse signal without trailing residual signal, the formation of a conductive path between electrodes in a gas medium is also relevant to other applications.
Based upon what is known about the prior art, there is a need to provide plasma waveguides, plasma horn antennas, and plasma coaxial waveguides that are capable of propagating electromagnetic waves in a desired direction or along a desired path. Not only would these waveguides and coaxial waveguides be reconfigurable with respect to the range of signal that could be propagated, e.g., speed, wavelength, etc., but these waveguides could also be designed to be more stealth, durable, and flexible than traditional metal waveguides and coaxial lines.
The present invention is drawn to various waveguides and coaxial waveguides which utilize plasma within an enclosed chamber for the conductive material. Specifically, a phase shifting plasma electromagnetic waveguide is disclosed comprising an elongated non-conductive enclosure defining a propagation path for directional electromagnetic wave propagation; a composition contained within the enclosure capable of forming a plasma, wherein the plasma has a skin depth along a surface within the enclosure such that the electromagnetic waves penetrate the skin depth and are primarily propagated directionally along the path; an energy source to form the plasma; and an energy modifying medium to modify the density of the plasma such that electromagnetic waves of various speeds may be propagated directionally along the path. In one embodiment, the enclosure further comprises a first open end and a second open end, wherein the first open end and the second open end are connected by a channel. The channel can be configured along the direction of wave propagation such that the electromagnetic waves penetrate the skin depth and travel within the channel. When an open channel is present, an optional second enclosure can be placed within the channel. Such a combination provides a phase shifting coaxial waveguide. The second enclosure preferably contains a plasma as well, though other structures such as metal can be used instead of a plasma containing enclosure.
Alternatively, a plasma electromagnetic waveguide horn antenna is disclosed comprising an elongated non-conductive enclosure defining a propagation path for directional electromagnetic wave propagation; a horn antenna structure electromagnetically coupled to the enclosure for emitting or receiving electromagnetic waves; a composition contained within the elongated enclosure capable of forming a plasma, wherein the plasma has a skin depth along a surface within the enclosure such that the electromagnetic waves penetrate the skin depth and are primarily propagated directionally along the path in the direction of the horn antenna; and an energy source to form the plasma.